The use of a SEPIC (Single-Ended Primary Inductance Converter) converter a fluorescent lamp ballast circuit is described in “SEPIC converter to perform power factor correction in a ballast for fluorescent lamps”, O. Busse, S. Mayer, B. Schemmel, A. Storm (Osram GmbH), IEEE Reference 01518852. This describes a standard circuit of a ballast for fluorescent lamps comprising a boost converter followed by a half bridge, one of the disadvantages of the boost converter being that the dc output voltage is always greater than the dc input voltage. The paper describes the use of a SEPIC converter which enables the dc output voltage driving the half bridge to be greater or less than the input voltage thus providing increased flexibility. However this arrangement is relatively complex.
An alternative topology is described in “A high-power-factor electronic ballast using a flyback push-pull integrated converter”, R. N. do Prado, S. A. Bonaldo, IEEE Transactions on Industrial Electronics, Vol. 46, No. 4, August 1999, IEEE reference 00778245. However this configuration has the disadvantage that, because of the flyback configuration, the input current waveform is discontinuous and hence the conducted emissions are high.
Another paper, “A practical comparison among high-power-factor electronic ballasts with similar ideas”, A. R. Seidel, F. E. Bisogno, T. B. Marchasan, and R. N. do Prado, IEEE Transactions on Industry Applications, Vol. 41, No. 6, November/December 2005, IEEE Reference 01542311, compares topologies including a boost half-bridge, a flyback half-bridge, a boost push-pull, and a flyback push-pull, recommending the flyback push-pull. Further background prior art can be found in U.S. Pat. No. 6,741,040, U.S. Pat. No. 6,690,122, EP 1 209 954A, GB 2,415,842A, U.S. Pat. No. 6,225,753, and “Coupled inductor design”, L. Dixon, UNITRODE Power Supply Design Seminar Manual SEM-900, Topic 8.
The field of lighting controllers continues to provide a need for lower cost, higher efficiency design.